Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 90: Metals and semiconductors: Epitaxy and growth
O 90.6: Talk
Friday, March 30, 2012, 11:45–12:00, A 060
Growth study: ultrathin GaN films on 6H-SiC(0001) — •Lena Neumann1, Jürgen Gerlach1, and Bernd Rauschenbach1,2 — 1Leibniz Institute of Surface Modification (IOM), D-04318 Leipzig, Germany — 2University Leipzig, Institute of Experimental Physics II, D-04103 Leipzig, Germany
Ultrathin gallium nitride (GaN) films were deposited using the ion-beam assisted molecular-beam epitaxy (IBA-MBE) technique. The influence of the nitrogen ion to gallium atom flux ratio (I/A ratio) at different substrate temperatures during the early stages of GaN nucleation and thin film growth directly on super-polished 6H-SiC(0001) substrates was studied. The deposition process was performed by evaporation of Ga and irradiation with hyperthermal nitrogen ions from a constricted glow-discharge ion source. The GaN growth in N- and Ga-rich regimes was investigated by in situ reflection high energy electron diffraction (RHEED) and scanning tunnelling microscopy (STM) measurements. The results show, that the I/A ratio has a major impact on the properties of the resulting ultrathin GaN films. The growth mode, the surface roughness, the degree of GaN coverage of the substrate and the polytype mixture depend notably on the I/A ratio. At the substrate temperature of 700 ∘C and the I/A ratio less than 1.6 the formation of islands developed through rapid coalescence into two-dimensional growth. A three-dimensional island growth mode is favoured at lower Ga fluxes, so that the I/A ratio > 1.6. The increase of the islands diameter to height ratio with the I/A ratio increasing was observed.